Re: [PATCH v3 net-next 0/6] ip: Batch flushing uncached routes per batched device unregistration.

[Chris Arges <carges@cloudflare.com>]

On 2026-10-01 20:47:12, Kuniyuki Iwashima wrote:
> Chris J Arges reported high RTNL contention during cleanup_net()
> caused by rt_flush_dev() and rt6_uncached_list_flush_dev() iterating
> over the global per-cpu uncached route lists for every netdev in
> dying netns [0].
> 
> This series resolves the issue by batching the uncached route
> cleanup after __rtnl_unlock() in netdev_run_todo()
> 
> [0]: https://lore.kernel.org/netdev/20260917-hash-bucket-route-lists-v3-0-30493a37b6eb@cloudflare.com/
> 
> 
> Changelog:
>   v3:
>     * Add patch 1 ~ 4
>     * Patch 6
>       * Unlink routes only when both devices are blackhole_netdev
>       * Clarify netdev_run_todo() does not run before
>         rt6_uncached_list is initialised
>       * Fix CONFIG_IPV6=n build
> 
>   v2: https://lore.kernel.org/netdev/20260929201546.1533268-1-kuniyu@google.com/
>     * Drop ->pre_exit_batch()
>     * Do batching after setting NETDEV_UNREGISTERED in netdev_run_todo()
> 
>   v1: https://lore.kernel.org/netdev/20260927202429.2452589-1-kuniyu@google.com/
> 
> 
> Kuniyuki Iwashima (6):
>   net: Order blackhole_netdev_init(), inet_init(), and inet6_init().
>   ipv4: Inline inet_blackhole_dev_init() to devinet_init().
>   net: Rename dev_isalive() to netif_is_alive().
>   xfrm: Check netif_is_alive() in xfrm_bundle_create() and
>     xfrm_create_dummy_bundle().
>   ipv4: Batch rt_flush_dev() in netdev_run_todo().
>   ipv6: Batch rt6_uncached_list_flush_dev() in netdev_run_todo().
> 
>  drivers/net/loopback.c    |  2 +-
>  include/linux/netdevice.h |  6 ++++++
>  include/net/ip6_route.h   |  7 +++++++
>  include/net/route.h       |  6 ++++++
>  net/core/dev.c            |  7 +++++++
>  net/core/dev.h            |  6 ------
>  net/core/net-sysfs.c      | 16 ++++++++--------
>  net/core/netdev_work.c    |  4 ++--
>  net/core/rtnetlink.c      |  2 +-
>  net/ipv4/devinet.c        | 17 +++++------------
>  net/ipv4/route.c          | 11 +++++++++--
>  net/ipv6/af_inet6.c       |  2 +-
>  net/ipv6/route.c          | 24 ++++++++++++++++--------
>  net/xfrm/xfrm_policy.c    |  4 ++--
>  14 files changed, 71 insertions(+), 43 deletions(-)
> 
> -- 
> 2.56.0.rc1.315.gc6ed9934b7-goog
>

I was able to run the v3 patchset locally and confirm it addresses
the original issue.

Tested-By: Chris J Arges <carges@cloudflare.com>

--chris